Controlled burst firing mechanism



sept. 7, 1965 s. D. slLsBY 3,204,529

CONTROLLED BURST FIRING MECHANISM Filed May 4, 1964 4 Sheets-Sheet 1 ATTORNEY Sept. 7, 1965 s. D. slLsBY CONTROLLED BURST FIRING MECHANISM Filed May 4, 1964 4 Sheets-Sheet 2 INVENTOR 5 mflgy D Elily BY www;

ATTORNEY sm. 7, w65

S. D. SILSBY CONTROLLED BURST FIRING MECHANISM Filed May 4, 1964 4 Sheets-Sheet 3 [NVENTOR Elunlgyllljly BY l ATTORNEY Sept. 7, 1965 s. D. slLsBY 3,204,529

' CONTROLLED BURST FIRING MECHANISM Filed May 4, 1964 4 Sheets-Sheet 4 Eig, Eipl 4' y I4 1G26 lNVENTOR #CA/I7 if. l

ATToNEY 2 United States Patent Oiice 3,264,529 Patented Sept. 7, 1965 CONTROLLED BURST FIRING MECSM Stanley D. Silsby, Granby, Mass., assigner to the United States of America as represented by the Secretary of the Army vFiled May 4, 1964, Ser. No. 364,868 7 Claims. (Cl. 89-14) (Granted under Title 35, US. Code (1952), sec. 266) The invention described herein may be manufactured and used by or for the Government for governmental purposes without the payment to me of any royalty thereon.

This invention pertains to firearms and is related more particularly to the ring mechanisms thereof.

It has been found that when a rifle is red automatically it climbs off target appreciably so as to be inefective after three or four rounds are iired and that a riie is much more effective and efficient if red in short controlled bursts.

It is, therefore, the object of this invention to provide for ries a tiring mechanism which is easily selected for semiautomatic, automatic and controlled -burst ring, and which is rugged in construction and positive in operatic-n.

The specific nature of the invention as well as other objects and advantages thereof will clearly appear from a description of a preferred embodiment as shown in the accompanying drawings in which:

FIG. l is a fragmentary, longitudinally cross-sectioned view of a rearm at the tiring mechanism showing the firing mechanism set for lsemiautomatic fire with the trigger in normal position;

FIG. 2 is a view taken along line 2 2 of FIG. l;

FIG. 3 is an enlarged view taken along line 3 3 of FIG. 2 and shows the trigger pulled and the hammer released;

FIG. 4 is a view similar to FIG. 3 but showing the hammer actuated by the bolt assembly to the retracted position;

FIG. 5 is an external view of the selector knob which is shown indexed for burst firing;

FIG. 6 is a view taken along `line 6*6 of FIG. 2 to show the opposite side of the tiring mechanism which is shown indexed for burst firing and with the hammer seared;

FIG. 7 is a view similar to FIG. 6 but shows the hammer displaced by the bolt assembly towards the retracted position;

FIG. 8 is a View similar to FIG. 3 but with the selector knob indexed for automatic tiring and shows the trigger pulled and the sears held clear of the counterwheel in the searing position to permit displacement of the hammer to the striking position;

FIG. 9 is a view taken along line 9-9 of FIG. 8 to show the hammer held retracted by the plunger lock;

FIG. 10 is a view taken along line Iii-10 of FIG. 9;

FIG. l1 is a View taken along line 11-11 of FIG. 5`

with the crankshaft shown in full;

FIG. 12 is a view taken along line 12-12 of FIG. 11; and

FIG. 13 is a perspective View of the hammer and sears assembly.

Shown in the gures is a rifle 12 having a receiver 14 in which a bolt assembly 16 is mounted for reciprocation between a forward battery position and a rearward recoil position. Bolt assembly 16 is of conventional two-piece type and consists of a carrier I3 and a bolt 20 mounted thereon for relative longitudinal displacement. Bolt 20 carries a firing pin 22.

A firing mechanism 24 is housed in receiver 14 below the path of movement of bolt assembly 16 and includes a hammer 26 which is pivotal between a retracted and a liring pin striking position. Hammer 26 is biased by a spring 28 to the striking position and is actuated to the retracted position by bolt assembly 16 during travel to the recoil position. Hammer 26 is releasably held in the retracted position by a plunger lock 30 which is cam actuated to release the hammer when bolt assembly 16 goes into recoil position by means of an operating rod 32 best shown in FIG. 10.

A RH sear 34 and a LH sear 36 are pivotally mounted side by side, as best shown in FIG. 13, on a shaft 38 which extends laterally through the free end of hammer 26. A pair of spring-biased balls 40, accommodated in mating wells 42 in hammer 26, press respectively against RH sear 34 and LH sear 36 so that each is biased outwardly, respective to the hammer, to a searing position. RH sear 34 is provided with an integral lug 44 which extends outwardly from the right side thereof adjacent the free end and LH sear 36 is similarly provided with a lug 46 which extends outwardly from the left side thereof. A RH arm 4S extends rearwardly from RH sear 34 adjacent the free end thereof and a LH arm 50 extends rearwardly from LH sear 36.

R and LH arms 4S and 50 engageably cooperate with a counterwheel 52 which is rotatingly mounted on a transverse shaft 54 located rearwardly of R and LH sears 34 and 36. Counterwheel 52 is provided with a total of nine sprockets 56 evenly spaced around the perimeter and each sprocket is provided with a radially extending side 58 at the leading edge, respective to rotation of the sprocket wheel in the clockwise direction, and a protuberance 60 which extends from the trailing edge. Sprockets 56 are spaced sufficiently to permit the projection of RH arm 48 and LH arm 5t) inbetween pairs thereof and RH sear 34 and LH sear 36 are so related to counterwheel 52 that when hammer 26 pivots to the retracted position the bottom edges of RH arm 48 and/ or LH arm 5t) are contactable with protuberance 60 Iof a related one of the sprockets 56 to cause rotation of counterwheel 52 one pitch in a clockwise direction. A ratchet 62, shown in FIG. 1, cooperatively engages sprockets 56 for holding counterwheel 52 against counterclockwise rotation. When hammer 26 is in the retracted position, RH arm 48 and LH arm S0 are extendible between two of the sprockets 56 with the top edge of RH arm 48 being contactable with side 58 of the related sprocket whereby hammer 26 is held in a seared position because the hammer cannot move towards striking position without rotating counterwheel 52 counterclockwise and counterclockwise rotation is prevented by ratchet 6 2.

As noted in FIGS. 6 and 7, sprockets 56 are divided into pairs, as indicated at 63, which are separated by a single sprocket, as indicated at 65. Sprockets 56 in the pairs 63 are each provided with a clearance 64 which is in registry with LH arm 50 and which is arranged so as to permit uninterrupted passage thereof past the related Sprocket when hammer 26 swings from the retracted to the striking position. Clearances 64 do not extend into protuberances 60 so that the protuberances are contactable by either or both RH arm 48 and LH arm 50, to rotate counterwheel S2 during retraction of hammer 26.

Hammer 26 is released from the seared position by a trigger 66 which is pivotally mounted on a transverse crankshaft 68 to be further described hereinafter. Trigger 66 includes a plunger-like extension 7i)` which is received by a well 72 that extends downwardly into the trigger from the top end thereof and such extension is biased upwardly by a spring 74. Extension 70 has a forwardly facing flat 76 at the outer end which is contactable with a bottom end 78 on RH sear 34 and a similar bottom end 79 on LH sear 36 so that, when trigger 66 is pulled to the tire position, both sears are forwardly displaced to actuate RH and LH arms 48 and 50 clear of counterwheel 52 for release of hammer 26. A cam surface 80 on the top of extension 70 is contactable with a cooperating cam surface 82 formed on the bottom of each RH sear 34 and LH sear 36 for displacing extension 70 downwardly, to prevent interference between trigger 66 and the sears when the sears are swung downwardly by retraction of hammer 26, and to permit displacement of the extension in back of bottom ends F78 and '79 when trigger 66 is released to its normal forward position.

RH sear 34 and LH sear 36 are selectively controlled to provide for semiautomatic, automatic and controlled burst firing through t-he cooperation of crankshaft 68 with a RH selector 84 under LH selector 86 which are pivotally mounted on the corresponding sides of trigger 66 at the upper end thereof. RH selector 84 and LH selector 86 are pivotally mounted approximately midway the lengths thereof on trigger 66 and formed respectively in the bottom portions of the R and LH selectors are cam slots S8 and 96. Cam slot 88 slidingly receives a RH throw 92 in crankshaft 68 and cam slot 96 similarly receives a LH throw 94. Cam slots 88 and 90 are formed so as to convert rotation lof crankshaft 68 to pivotal displacement of the R and LH selectors 84 and 86 as hereinafter described. Crankshaft 68 is manually rotated by a selector knob 96.

The upper portion of RH selector S4 forms a finger 98 which is actuatable rearwardly through pivotal displacement of such selector by crankshaft 68 to where lug 44 on RH sear 34 makes sliding contact with such finger during pivotal displacement of hammer 26 so as to hold the RH sear in its release position. The yup-per portion of LH selector 86 forms a similar finger 100 which is actuatable by crankshaft 68 to a position so as to make sliding contact with lug 46 on LH sear 36 to similarly hold such sear in its release position, during displacement of hammer 26, when crankshaft 68 is indexed to position LH sear for such contact.

RH selector 84 and LH selector 86 are so arranged in cooperation with crankshaft 68 that, when selector knob 96 is indexed for automatic fire, RH sear 34 and LH sear 36 are both held in their release positions by the associated selectors 84 and 86 during cyclic reciprocation of ham-mer 26 and so long as trigger 66 is held in the fire position, and so that when the selector knob is indexed for burst tiring, the RH sear only is held thus in the release position. When selector knob 96 is indexed for semiautomatic fire, RH selector 84 is displaced by crankshaft 68 so as to be free of contact with RH sear 34, whereby such sear is operable to the searing position each firing cycle, and LH selector 86 is positioned for contact with LH sear 36 to hold such sear in the release position when trigger 66 -is held in the fire position.

Operation To fire riiie 12 automatically, selector knob 96 is indexed in the automatic position where A on the selector knob is indexed with a reference mark on receiver 14 as shown in FIG. 5. Rifle 12 is ready to fire when hammer 26 is held cocked by the engagement of arms 48 and 50 with one of the sprockets 56 and trigger 66 is in its normal forward position. Firing is commenced by squeezing back on trigger 66 whereby, trigger extension 70 is actuated forwardly .against bottom ends 78 and 79 of RH sear 34 and LH sear 36, respectively, pulling R and LH arms 48 and 56 of such sears clear of the engaged one of the sprockets 56. This frees hammer 26 which swings to strike ring pin 22 for discharge of the chambered cartridge (not shown). Responsive to the discharge, bolt assembly i6 is energized for travel to and from the recoil position. During recoil travel of bolt assembly 16, hammer 26 is displaced thereby to the retracted position where it is releasably latched by plunger lock 30. When bolt assembly i6 returns to battery position, operating rod 32 is actuated by the bolt assembly to actuate plunger lock 3ft for release of hammer 26. When hammer 26 swings to and from its striking position, lugs 44 and 46, travel respectively, along fingers 98 and iti() of the R and LH selectors 84 and 86. Fingers 98 and 10@ are positioned respectively by R and LH throws 92 and 94 of crankshaft 68 so that lugs 44 and 46 of R and LH sears 34 and 36 slidingly contact the related fingers during displacement of hammer 26 and as long as trigger 66 is held pulled, to hold the sears in their release positions free of counterwheel 52. Consequently, when hammer 26 is released by plunger lock 30, it is free to proceed uninterrupted to strike firing pin 22 and fire another round. Firing will cont-inne until trigger 66 is released to its normal position, whereupon R and LH sears 34 and 36 are free to be pivoted by spring biased balls 46 to their searing positions with R and LH arms 48 and 50 engaging one of the sprockets, after release from plunger lock 30, to hold hammer 26 in the cocked position.

To fire rie 12 semi-automatically, selector knob 96 is indexed in the semi-automatic position, identified by S on the selector knob, whereby, crankshaft 68 is turned to where RH throw 92 positions RH selector 84 to where RH finger 98 is held free of contact by lug 44 and LH throw 94 positions LH arm 56 to where it is contactable by lug 46 to hold LH sear 36 in the release position during displacement of hammer 26 and so long as trigger 66 is held in the fire position. Thus, when trigger 66 is pulled to release hammer 26, by acting against bottom ends 78 and 79 of RH sear 34 and LH sear 36, respectively, bolt assembly 16 is energized by the resulting discharge. As the energized bolt assembly 16 moves to recoil position hammer 26 is swung to its retracted position causing RH arm 48 to make contact with protuberance 66 of the next successive sprocket 56 on counterwheel 52 and thereby rotate the counterwheel one pitch in the clockwise direction. Hammer 26 is momentarily held by plunger lock 30 in the retracted position until bolt assembly 16 returns to battery position and during this time, arm 48 of RH sear 34 is pressed by the related one of ithe balls 40 between two of the sprockets 56.

When hammer 26 is Ireleased by plunger lock 30 it is almost immediately sea-red in the cocked position by contact of RH arm 48 with side 53 of the related sprocket 56 and the action of ratchet 62 which presents counterclockwise rotation of counterwheel 52 by the bias of the hammer. When hammer 26 swung to its retracted position, bottom ends '78 and 79 of RH sear 34 and LH sear 36, respectively, pressed downwardly on trigger extension 70 which was depressed thereby into trigger 66 to prevent interference with :the sears. When trigger 66 is released to its normal position, extension 79 snaps up in back of bottom ends 7S and '79 ready to actuate RH sear 34 for release of hammer 26 the next time that the trigger is pulled.

To fire rie 12 in a controlled burst, selector knob 96 is indexed in the burst position which is identified by B on counterwheel 52 whereby, crankshaft 68 is positioned so that throws 92 and 94 are located to hold RH sear 34 in its release position after trigger 66 is pulled but positions LH selector 86 clear of LH sear 36 so that such sear has operational cooperation with the counterwheel. Thus, each time hammer 26 is swung to the retracted position, arm 50 of LH sear 36 contacts successive ones of the sprockets 56 to sequentially rotate counterwheel 52 one pitch. If the sprocket 56 coming up into engaging relationship with arm 50 has a clearance 64, hammer 26 will proceed uninterrupted from the retracted to the striking position after being released by plunger lock 30. However, the burst will stop when LH arm 50 comes into cooperation with a sprocket 56 which does not have a clearance 64. Thus, as sprockets 56 consist of pairs thereof with clearances 64, separated by a single sprocket without a clearance, rifle 12 will fire a burst of three rounds each time trigger 66 s pulled. If fourround bursts are desired, sprockets 56 will be arranged so that there are groups of three sprockets with clearances 64 separated by a single sprocket without a clearance.

Although a particular embodiment of the invention has been described in detail herein, it is evident that many variations may be ydevised within the spirit and scope thereon and the following claims are intended to include such variations.

Iclaim:

l. In a firearm having a bolt reciproc'able between a battery and a recoil position and provided with a firing pin, a firing mechanism including a hammer pivotally displaced to a retracted posit-ion by the bolt during travel to the recoil position and being spring biased to a striking position, a first sear and a second sear pivotally mounted side by side on said hammer at the free end thereof, a trigger pivotal between a normal and a re position, a counterwheel having operation-al cooperation with said first and second sears for rotary displacement thereby and for searing said hammer in a cocked position between the retracted and striking positions, means for selectively displacing said first and second sears between searing and release positions during pivotal displacement of said hammer to provide for semi-automatic, auto-matic and controlled-burst firing, a lock4 for releasably holding said hammer in the retracted position, and an operating rod operationally disposed between said bolt and said loc-k for releasing said hammer therefrom when said bolt is in the battery position.

2. The firing mechanism as detiined in cla-im 1 wherein said first and second sears are each provided with a Ibottom end contactable by said trigger for displacing said sear to the release positions for release of said hammer when said trigger is actua-ted from the normal to the fire position, and wherein said bottom end of each of said sears is elevated free of said trigger when said hammer is displaced to and .from the striking position.

3. The firing mechanism as defined in claim 1 wherein said first and second sears are each provided with an arm extendable into engaging relationship with said counter- Wheel when the respective one of said first and second sears is in the searing position, and said counterwheel is provided with a plurality of sprockets positioned around the perimeter thereof so as to be successively contacta-ble by said arm of either or both of said first and second sears during displacement of said hammer to the retracted position to rotate said hammer one pitch each operating cycle of the firearm, said sprockets bei-ng spaced so as to receive said arm of either or both of said first and second sears between pairs of said sprockets when said hammer is in the retracted position and said first and second sears are in the searing positions, and a ratchet having operational cooperation with said sprockets to hold said counterwheel against counter-rotation by said first and second sears for searing said hammer in `the cocked position.

4. The firing mechanism as defined in claim 3 wherein said means include a first and a second selector pivotally mounted on said trigger for respective cooperation with said first and second sears to control displacement thereof respective to the release and searing positions thereat during pivotal displacement of said hammer, and .a crankshaft having a first and a second throw respectively cooperating with said first and second selectors for selective displacement thereof to control the operation of said first and second sears for producing automatic, semi-automatic and controlledaburst fire.

5. The firing mechanism as defined in claim 4 wherein said first and second sears are respectively provided with a lug on one of t-he sides thereof, and said first and second selectors are respectively provided with a finger displaceable against the related lug for sliding contact therewith to hold the respective one of said first and second sears in the release position clear of said sprockets during pivotal displacement of said hammer when said crankshaft is indexed to hold one of said first and second sears inoperative. 6. The firing mechanism as defined in claim 5 wherein said sprockets include groups of .a predetermined number of sprockets separated by a single sprocket, and including in each of said sprockets in said groups a clearance having registry with said arm of said second sear when said hammer is in the retracted position and said second sear is in the searing position to permit uninterrupted passage of said hammer from the retracted to the striking .position when said first sear is held in the release position and said second Sear is in the searing position.

7. The firing mechanism as defined in claim 6 wherein said first and second throws of said crankshaft are so related and have ysuch operational cooperation with the respective ones of said first and second selectors that when said crankshaft is indexed for automatic fire said first and second selectors are positioned so that said fingers thereof slidingly contact said lugs to hold said first and second sears in the release positions thereof during displacement of said hammer when said trigger is held in the fire position, that when said crankshaft is indexed for semi-automatic fire said second selector is positioned so that said finger of said second selector sl-idingly contacts said lug of lsaid second sear to hold said second sear in the release position and said first selector is positioned so that said finger thereon is clear of contact with said lug of said first sear during displacement of said hammer when said trigger is in the fire posit-ion7 and that when said crankshaft is indexed for controlled burst firing said seco-nd selector is positioned so that said finger thereof is clear of contact with said l=ug yof said second sear and said first selector is in position so that said arm thereof slidingly contacts said lug of said first sear to hold said sear in the release position thereof during displacement of said hammer when said trigger is in the fire position.

No references cited.

BENJAMIN A. BORCHELT, Primary Examiner. 

1. IN A FIREARM HAVING A BOLT RECIPROCABLE BETWEEN A BATTERY AND A RECOIL POSITION AND PROVIDED WITH A FIRING PIN, A FIRING MECHANISM INCLUDING A HAMMER PIVOTALLY DISPLACED TO A RETRACTED POSITION BY THE BOLT DURING TRAVEL TO THE RECOIL POSITION AND BEING SPRING BIASED TO A STRIKING POSITION, A FIRST SEAR AND A SECOND SEAR PIVOTALLY MOUNTED SIDE BY SIDE ON SAID HAMMER AT THE FREE END THEREOF, A TRIGGER PIVOTAL BETWEEN A NORMAL AND A FIRE POSITION, A COUNTERWHEEL HAVING OPERATIONAL COOPERATION WITH SAID FIRST AND SECOND SEARS FOR ROTARY DISPLACEMENT THEREBY AND FOR SEARING SAID HAMMER IN A COCKED POSITION BETWEEN THE RETRACTED AND STRIKING POSITIONS, MEANS FOR SELECTIVELY DISPLACING SAID FIRST AND SECOND SEARS BETWEEN SEARING AND RELEASE POSITIONS DURING PIVOTAL DISPLACEMENT OF SAID HAMMER TO PROVIDE FOR SEMI-AUTOMATIC, AUTOMATIC AND CONTROLLED-BURST FIRING, A LOCK FOR RELEASABLY HOLDING SAID HAMMER IN THE RETRACTED POSITION, AND AN OPERATING ROD OPERATIONALLY DISPOSED BETWEEN SAID BOLT AND SAID LOCK FOR RELEASING SAID HAMMER THEREFROM WHEN SAID BOLT IS IN THE BATTERY POSITION. 